Melt the butter in a saucepan over medium heat. Add the flour and mix until well blended. Cook for 3 to 4 minutes. Gradually pour in the milk, stirring constantly, until well blended. Bring to a boil, then lower the heat to a simmer and cook until slightly thickened, about 10 minutes. Add the sugar and salt and stir until incorporated. Serve the white sauce over warmed potatoes.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.